Benzoheterocyclic compounds

ABSTRACT

Novel 4-oxoquinoline-3-carboxylic acid compounds of the formula: ##STR1## wherein R 3  is C 1  -C 6  alkyl and R F  is C 1  -C 6  alkyl, and a pharmaceutically acceptable salts thereof, said compounds having excellent antimicrobial activity and hence being useful as an antimicrobial agent, and a pharmaceutical composition containing said compound as an active ingredient.

This is a Continuation-in-part application of U.S. Ser. No. 017,247 filed on Feb. 20, 1987, now abandoned.

The present invention relates to novel antimicrobial benzoheterocyclic compounds of the formula [I]: ##STR2## wherein R³ is C₁ -C₆ alkyl and R^(F) is C₁ -C₆ alkyl, and pharmaceutically acceptable salts thereof.

The benzoheterocyclic compounds of the formula [1] and salts thereof have excellent antibacterial activities against various gram positive and gram negative bacteria, and are useful for the treatment of various infectious diseases induced by various bacteria in human, other animals and fish and are also useful as an external antimicrobial or disinfectant agent for medical instruments of the like.

PRIOR ART

There are many literatures which disclose 4-oxoquinoline-3-carboxylic acid derivaties useful as antibacterial agents. Among these literatures, U.S. Pat. Nos. 4,547,503 and 4,544,658 (=European Patent Publication Nos. 113092 and 113093, respectively) and U.S. Pat. No. 4,559,342 disclose 1-cyclopropyl-7-piperazino-dihydroquinoline carboxylic acid derivatives of the formula: ##STR3##

U.S. Pat. No. 4,563,459 (=German Patent No. 3248507 and Japanese Patent First Publication (Kokai) No. 130802/1984) discloses 1-cyclopropyl-dihydroquinoline carboxylic acid derivatives of the formula: ##STR4## wherein R₁ is H, F, Cl, Br or NO₂, R² is H, Cl, F or NR³ R⁴ wherein R³ and R⁴ together may form 5- or 6-membered saturated or partly unsaturated heterocycles.

Australian Patent Publication No. 8,542,762 (=South African Patent No. 8504087 discloses 1-cyclopropyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid derivatives of the formula: ##STR5## wherein R¹ is H, CH₃, C₂ H₅ or --CH₂ CH₂ OH, R² is H, Cl or F.

Australian Patent Publication No. 8543293 (=German Patent No. 3420743) discloses 7-amino-1-cyclopropyl-3-quinoline carboxylic acid derivatives of the formula: ##STR6## wherein X¹ and X² are each Cl or F, R¹ and R² may combine together with N atom to form a 5- or 6-membered heterocyclic ring.

U.S. Pat. No. 4,588,726 (=German Patent No. 3420770) and Australian Patent Publication No. 8543206 (=German Patent No. 3420798) disclose 1-cyclopropyl-7-piperazinyldihydroquinoline carboxylic acid derivatives of the formula: ##STR7## wherein R is oxo or phenyl, etc. and R² is H or F.

U.S. Pat. No. 4,620,007 (=Japanese Patent First Publication (Kokai) No. 74667/1983) discloses quinolone carboxylic acid derivatives of the formula: ##STR8## wherein R is H, CH₃, C₂ H₅, etc.

U.S. Pat. No. 4,556,658 (=Japanese Patent First Publication (Kokai) No. 212474/1984) discloses quinolone carboxylic acid derivatives of the formula: ##STR9## wherein R¹ R² N-- may form heterocyclic groups.

Portugal Patent No. 80546 (=European Patent Publication No. 195841) discloses quinolone carboxylic acid derivatives of the formula: ##STR10## wherein A is N or CH, R is H or alkyl, R¹ is C₃ -C₆ cycloalkyl, R² is H or NH₂, Z is halogen, a group of the formula: ##STR11## etc.

Similar 1-cyclopropyl-7-heterocyclic group-substituted dihydroquinoline carboxylic acid derivatives are also disclosed in other many literatures such as European Patent Publication Nos. 153828 and 178388, South African Patent No. 8106080, U.S. Pat. No. 4,563,448, and Australian Patent Publication No. 8424284,

However, the compounds disclosed in these literatures are different from the compounds of this invention in view of having no alkyl substituent at 8-position.

There are disclosed 1-cyclopropyl-7-heterocyclic group-8-alkyl-dihydroquinoline carboxylic acid derivatives in some literatures. For instance, Japanese Patent First Publication (Kokai) No. 126271/1985 (=Portugal Patent 79616) and Belgian Patent 899,399 disclose quinolone carboxylic acid derivatives of the formula: ##STR12## wherein R is H, CH₃, p-nitobenzyl or p-aminobenzyl, Y is Cl, F, or CH₃, but this literature does not disclose any specific example of 8-CH₃ derivative (all examples are concerned with 8-Cl or 8-F derivatives).

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide novel benzoheterocyclic compounds of the formula [1] and salts thereof which have excellent antimicrobial activity and excellent absorbability. Another object of the invention is to provide a pharmaceutical composition containing as an active ingredient a compound of the formula [1] or a pharmaceutically acceptable salt thereof, which is useful for the treatment of various infectious diseases. These and other objects of the invention will be apparent to persons skilled in the art from the following description.

DETAILED DESCRIPTION OF THE INVENTION

The novel benzoheterocyclic compounds of the present invention have the formula [1] as mentioned above and include pharmaceutically acceptable salts thereof.

In the specification, the term "halogen atom" includes fluorine, chlorine, bromine or iodine atom.

The term "C₁ -C₆ alkyl" includes straight chain or branched chain C₁ -C₆ alkyl groups, such as methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl, etc.

The compounds of the present invention of the above general formula [1] can be prepared by various processes and preferably prepared, for example, by the processes as shown in the following reaction schemes. ##STR13## wherein R³ is as defined above, R^(2') is a halogen atom or a group of the formula: ##STR14## (R^(F) is as defined above, and R is hydrogen atom, benzyl or ethoxycarbonyl), R⁴ is a group of the formula --COR⁹ (wherein R⁹ is a lower alkyl) or a group of the formula --COOR¹⁰ (wherein R¹⁰ is a lower alkyl), R⁵ is a lower alkyl, R⁶ is a group of the formula: ##STR15## (wherein R¹¹ and R¹² are each a lower alkyl) or a lower alkoxy, X² and X³ are each a halogen atom, R⁷ and R⁸ are each a lower alkyl.

The halogenation of the compound [2] is carried out by reacting with a halogenating agent in the presence or absence of a solvent. The solvent includes aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), halogenated hydrocarbons (e.g. dichloromethane, chloroform, carbon tetrachloride, etc.), ethers (e.g. dioxane, tetrahydrofuran, diethyl ether, etc.), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and the like. The halogenating agent may be any conventional halogenating agents which can convert hydroxy in carboxy group into a halogen atom, and includes, for example, thionyl chloride, phosphorus oxychloride, phosphorus oxybromide, phosphorus pentachloride, phosphorus pentabromide, and the like. The amounts of the compound [2] and the halogenating agent are not specified, but, in case of using no solvent, the halogenating agent is usually used in a large excess amount, and in case of using a solvent, the halogenating agent is usually used in an amount of at least 1 mole, preferably 2 to 4 moles, per 1 mole of the compound [2]. The reaction temperature and the reaction period of time are not specified, either, but the reaction is usually carried out at a temperature of from room temperature to 100° C. for 30 minutes to 6 hours.

The reaction of the compound [3] and the compound [4] is carried out in a suitable solvent in the presence of a basic compound. The solvent may be any conventional solvents unless they give any undesirable effect on the reaction, and includes, for example, water, ethers (e.g. diethyl ether, dioxane, tetrahydrofuran, monoglyme, diglyme, etc.), alcohols (e.g. methanol, ethanol, isopropanol, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), aliphatic hydrocarbons (e.g. n-hexane, heptane, cyclohexane, ligroin, etc.), amines (e.g. pyridine, N,N-dimethylaniline, etc.), halogenated hydrocarbons (e.g. chloroform, dichloromethane, carbon tetrachloride, etc.), aprotic polar solvents (e.g. DMF, DMSO, hexamethylphosphoramide (HMPA), etc.), and a mixture of these solvents. The basic compound includes inorganic bases (e.g. metallic sodium, metallic potassium, metallic magnesium, sodium hydride, sodium amide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, etc.), metal alcoholates (e.g. sodium methylate, sodium ethylate, etc.), and organic bases (e.g. pyridine, piperidine, quinoline, triethylamine, N,N-dimethylaniline etc.). The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from room temperature to 120° C., for 0.5 to 15 hours. The compound [4] is usually used in an amount of at least 1 mole, preferably 1 to 2 moles, per 1 mole of the compound [3]. The basic compound is usually used in an amount of at least 1 mole, preferably 1 to 2 moles, per 1 mole of the compound [3].

The compound [5] wherein R⁴ is the group: --COR⁹ is subjected to the reaction for removal of the group: --COR⁹ in a suitable solvent in the presence of a basic compound. The solvent includes ethers (e.g. diethyl ether, dioxane, tetrahydrofuran, monoglyme, diglyme, etc ), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), aliphatic hydrocarbons (e.g. n-hexane, heptane, cyclohexane, etc.), aprotic polar solvents (e.g. DMF, DMSO, HMPA, etc.), and the like. The basic compound includes ammonia gas, aqueous ammonia, primary or secondary amines (e.g. ethylamine, diethylamine, piperidine, etc.), and the like. The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from room temperature to 100° C., for 1 to 20 hours.

The compound [5] wherein R⁴ is a group: --COOR¹⁰ is subjected to the reaction for removal of the group: --COOR¹⁰ in an aqueous solution in the presence of an acid catalyst. The acid catalyst includes mineral acids (e.g. hydrochloric acid, sulfuric acid, etc.) and organic acids (e.g. p-toluenesulfonic acid, etc.). The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from room temperature to 100° C., for 1 to 20 hours.

The reaction of the R⁴ group-removed compound and the compound [6] is carried out in a suitable solvent. The solvent may be any solvents which are used in the above reaction for the removal of the R⁴ group. The reaction is usually carried out at a temperature of from 0° to 200° C., preferably from 0° to 150° C., for 0.5 to 10 hours. The compound [6] is usually used in an equimolar to large excess amount, preferably 1 to 2 moles per 1 mole of the compound [5]. In case of using a compound [6] wherein R⁶ is a lower alkoxy group, the reaction may also be carried out by using acid anhydrides (e.g. acetic anhydride) as a solvent as well as above-mentioned solvents at a temperature of from 0° to 200° C., preferably 0° to 170° C.

The reaction of the compound [7] and the compound [8] is carried out in a suitable solvent The solvent may be any conventional solvents unless they give any undesirable effect on the reaction, and includes, for example, alcohols (e.g. methanol, ethanol, propanol, etc.), ethers (e.g. diethyl ether, dioxane, tetrahydrofuran, monoglyme, diglyme, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), aliphatic hydrocarbons (e.g. n-hexane, heptane, cyclohexane, ligroin, etc.), halogenated hydrocarbons (e.g. chloroform, methylene chloride, carbon tetrachloride, etc.), aprotic polar solvents (e.g. DMF, DMSO, HMPA, etc.), and the like. The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from room temperature to 100° C., for 0.5 to 15 hours. The compound [8] is usually used in an amount of at least 1 mole, preferably 1 to 2 moles, per 1 mole of the compound [7]. In the reaction, a basic compound may optionally be added and such basic compound may be any basic compounds which are used in the above reaction of the compound [3] and the compound [4].

The cyclization of the compound [9] is carried out in a suitable solvent in the presence of a basic compound. The solvent may be any conventional solvents unless they give any undesirable effect on the reaction, and includes, for example, ethers (e g. diethyl ether, dioxane, tetrahydrofuran, monoglyme, diglyme, etc.), aliphatic hydrocarbons (e.g. n-hexane, heptane, ligroin, etc.), halogenated hydrocarbons (e.g. chloroform, methylene chloride, carbon tetrachloride, etc.), aprotic polar solvents (e.g DMF, DMSO, HMPA, etc.), and the like. The basic compound includes inorganic bases (e.g. metallic sodium, metallic potassium, sodium hydride, sodium amide, sodium hydroxide, potassium hydroxide, etc.), metal alcoholates (e.g. sodium methylate, sodium ethylate, etc.), and organic bases (e.g. 1,8-diazobicyclo[5.4.0]undecene-7 (DBU), N-benzyltrimethylammonium hydroxide, tetrabutylammonium hydroxide, etc.). The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from room temperature to 120° C., for 0.5 to 5 hours The basic compound is usually used in an amount of at least 1 mole, preferably 1 to 2 moles, per 1 mole of the compound [9].

The hydrolysis of the compound [10] can be carried out under the conditions of conventional hydrolysis, for instance, in the presence of a basic compound (e.g sodium hydroxide, potassium hydroxide, barium hydroxide, potassium carbonate, etc.), a mineral acid (e.g. sulfuric acid, hydrochloric acid, nitric acid, etc.) or an organic acid (e.g. acetic acid, aromatic sulfonic acids, etc.) in a solvent such as water, alcohols (e.g methanol, ethanol, isopropanol, etc.), ketones (e.g. acetone, methyl ethyl ketone, etc.), ethers (e.g. dioxane, ethylene glycol, etc.), acetic acid, or a mixture thereof. The reaction is usually carried out at a temperature of from room temperature to 200° C., preferably from room temperature to 150° C., for 0.1 to 30 hours. By the reaction, there is produced the compound [1a]. ##STR16## wherein R, R³ and R^(F) are as defined above, X⁴ is a halogen atom, and R¹³ is hydrogen atom or a group of the formula: ##STR17## (wherein R¹⁴ and R¹⁵ are each an alkyl).

The reaction of the compound [1b] and the comound [11] is carried out in an inert solvent, wherein both compounds are used in a wide range of ratio, and the compound [11] is usually used in an amount of at least 1 mole, preferably 1 to 5 moles, per 1 mole of the compound [1b]. The solvent includes, for example, water, alcohols (e.g. methanol, ethanol, isopropanol, butanol, amyl alcohol, isoamyl alcohol, etc.), aromatic hydrocarbons (e.g benzene, toluene, xylene, etc.), ethers (e.g. tetrahydrofuran, dioxane, diglyme, etc.), dimethylacetamide, DMF, DMSO, HMPA, N-methylpyrrolidone, and a mixture thereof. Among these solvents, the preferred one is DMF, DMSO, HMPA, and N-methylpyrrolidone. The reaction may also be carried out in the presence of an acid-removing agent, such as inorganic carbonates (e.g. sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc.) or organic bases (e.g. pyridine, quinoline, triethylamine, etc.). An alkaline methal halide (e.g. potassium fluoride, etc.) may also be added in the reaction mixture. The reaction is usually carried out under a pressure of from 1 to 20 atm., preferably from 1 to 10 atm., at a temperature of from room temperature to 250° C., preferably from room temperature to 200° C., for 0.5 to 30 hours.

The compound [1b'] wherein R¹³ is a group: ##STR18## can be converted into the corresponding compound [1b'] wherein R¹³ is hydrogen atom by treating the former compound with an acid or a base to decompose the chelate compound. The acid includes mineral acids (e.g. hydrochloric acid, sulfuric acid, etc ) and organic acids (e.g. acetic acid, p-toluenesulfonic acid, etc.) and the base includes mineral bases (e.g. sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, potassium carbonate, etc.) and organic bases (e.g. triethylamine, etc.). The reaction is preferably carried out at a temperature of from 0° C. to 150° C., preferably from 0° C. to 100° C. The acid or the base may be used in an amount of at least 1 mole, preferably 1 to 10 moles, per 1 mole of the starting compound.

The compound [1a] in which R^(2') is a group of the formula: ##STR19## and R is benzyl group can be converted into the compound [1a] in which R is hydrogen atom by treating the former compound in a suitable solvent such as water, a lower alcohol (e.g. methano, ethanol, isopropanol, etc.), an ether (e.g. dioxane, tetrahydrofuran, etc.), acetic acid, or a mixture thereof, in the presence of a catalyst for a catalytic reduction such as palladium carbon, palladium black, or the like, under a hydrogen pressure of from 1 to 10 atm., at a temperature of from 0° to 100° C., for 0.5 to 10 hours (wherein a mineral acid such as hydrochloric acid may be added to the reaction mixture), or by heating the former compound in an aqueous hydrobromic acid solution to remove the benzyl group.

The compound [1a] or [1j] in which R^(2') is a group of the formula: ##STR20## and R is an ethoxycarbonyl group can be converted into the compound [1a] or [1j] in which R is hydrogen atom by hydrolyzing the former compound under the same reaction conditions as employed in the hydrolysis of the above compound [10].

In the reaction scheme-I, the starting compounds of the formula [2] are novel or known compounds, which can be prepared, for example, by the process as shown in the following reaction scheme-V. ##STR21## where R^(2'), and X² are as defined above, X⁵ and X⁶ are each a halogen atom, R¹⁹ is hydrogen atom or a lower alkyl and R²⁰ is a lower alkyl, in which R¹⁹ and R²⁰ may be taken together to form a 5- to 7- membered ring, and M is an alkaline metal (e.g. sodium, potassium, etc.) or a metal (e.g. silver, calcium, copper, etc.).

In case that R¹⁹ and R²⁰ of the compound [16] are taken together to form a 5- to 7-membered ring, R¹⁹ of the compound [20] is --R¹⁹ --R²⁰ --H.

The compound [16] can be prepared by reacting a starting aniline derivative of the formula [14] with a halogenating agent and then reacting the resultant compound of the formula [14a] with a thio compound of the formula [15].

The reaction of an aniline derivative [14] and a halogenating agent is usually carried out in a suitable solvent. The solvent may be any conventional solvents unless they give any undesirable effect on the reaction, and includes, for example, halogenated hydrocarbons (e.g. chloroform, dichloromethane, etc.), ethers (e.g. dioxane, diethyl ether, tetrahydrofuran, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), lower alcohols (e.g. methanol, ethanol, isopropanol, etc.), and polar solvents (e.g. DMSO, HMPA, acetonitrile, etc.). The halogenating agent may be any conventional halogenating agents and includes, for example, N-bromosuccinimide, N-chlorosuccinimide, sodium hypobromite, sodium hypochlorite, bleaching powder, thionyl chloride, tert-butyl hypochlorite, and the like. The halogenating agent is usually used in an amount of at least 1 mole, preferably 1 to 6 moles, per 1 mole of the starting material. The reaction is usually carried out at a temperature of from -78° C. to room temperature, preferably from -60° to 15° C., and usually completes within a few minutes. By the reaction, there is produced the intermediate of the formula [14a]. While the resultant compound [14a] may be separated from the reaction mixture to provide it for a subsequent reaction, the reaction mixture is usually provided for the reaction with a thio compound of the formula [15] without separating it from the reaction mixture.

The reaction of the compound [14a] and the compound [15] is carried out in the same solvent as above-mentioned in the presence of a basic compound. The basic compound includes inorganic bases (e.g. potassium carbonate, sodium carbonate, sodium hydroxide, sodium hydrogen carbonate, sodium amide, sodium hydride, etc.), and organic bases such as tertiary amines (e.g. triethylamine, tripropylamine, pyridine, quinoline, etc.). The compound [15] is usually used in an amount of at least 1 mole, preferably 1 to 1.5 moles, per 1 mole of the compound [14a]. The reaction is usually carried out at a temperature of from room temperature to 150° C., preferably from room temperature to 100° C., for 1 to 50 hours. The reaction of the compound [16] and the compound [17] is carried out in a suitable solvent in the presence or absence of a basic compound. The solvent includes water, alcohols (e.g. methanol, ethanol, isopropanol, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), ethers (e.g. dioxane, tetrahydrofuran, diglyme, etc ), polar solvents (e.g. DMF, DMSO, HMPA, N-methylpyrrolidone, etc.), or a mixture thereof. The basic compound includes inorganic carbonates (e.g. sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc.), organic bases (e.g. pyridine, quinoline, triethylamine, etc.), phase transition catalysts (e.g. phenyltriethylammonium chloride, tetramethylammonium chloride, etc.), and the like. The compound [17] is usually used in an amount of at least 1 mole, preferably 1 to 2 moles, per 1 mole of the compound [16]. The reaction is usually carried out at a temperature of from room temperature to 200° C., preferably from room temperature to 180° C., for 0.5 to 10 hours.

The desulfuration of the compound [18] for preparing the compound [19] is usually carried out in a solvent in the presence of a suitable catalyst. The catalyst includes, for example, aluminum-amalgam, lithium-lower alkylamine, Raney nickel, Raney cobalt, triethyl phosphite, triphenyl phosphine, and the like, and preferable one is Raney nickel. The solvent includes alcohols (e.g. methanol, ethanol, isopropanol, etc.), ethers (e.g. diehtyl ether, dioxane, tetrahydrofuran, etc.), and the like. The reaction is usually carried out at a temperature of from 0° to 200° C., preferably from room temperature to 100° C., for 10 minutes to 5 hours. The catalyst is usually used in an amount of from 1 to 10-fold by weight of the compound [18].

The reaction of converting the compound [19] into the compound [20] is carried out by reacting the compound [19] with a metallic salt of nitrous acid (e.g. sodium nitrite, potassium nitrite, etc.) in a suitable solvent in the presence of an acid, and then reacting the resultant product with a metal halide (e.g. potassium iodide, copper (I) chloride, copper (I) bromide, etc.) without separating it from the reaction mixture. The acid includes mineral acids such as hydrochloric acid, sulfuric acid and hydrobromic acid. The solvent includes water, alkanoic acids (e.g. acetic acid, etc.), ethers (e.g. dioxane, tetrahydrofuran, etc.), aromatic hydrocarbons (e.g. benzen, toluene, xylene, etc.), alcohols (e.g. methanol, ehtanol, isopropanol, etc.), halogenated hydrocarbons (e.g. chloroform, dichloromethane, dichloroethane, etc.), aprotic polar solvents (e.g. DMF, DMSO, HMPA, etc.), and a mixture thereof. The metallic salt of nitrous acid and the metal halide each is usually used in an amount of at least 1 mole, preferably 1 to 1.5 moles, per 1 mole of the compound [19]. The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from 0° to 100° C., for 10 minutes to 5 hours.

The hydrolysis of the compound [20] can be carried out in the presence of a suitable hydrolysis catalyst, for instance, a mineral acid (e.g. sulfuric acid, hydrochloric acid, hydrobromic acid, phosphoric acid, etc.) or a basic compound (e.g. sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, etc.) in the presence or absence of a solvent. The solvent includes, for example, water and a mixture of water and a lower alcohol (e.g. methanol, ehtanol, etc.). The reaction is usually carried out at a temperature of from 50° to 200° C., preferably 70° to 180° C., for 1 to 10 hours.

In the reaction scheme-II, the compounds of the formula [1b] wherein R¹³ is a group: ##STR22## can be prepared, for example, by the process as shown in the following reaction scheme-VI. ##STR23## wherein R³, X⁴, R¹⁴ and R¹⁵ are as defined above, R^(5') is a lower alkyl or hydrogen atom, R^(13') is a group: ##STR24## and R²¹ is a lower alkyl.

The reaction of the compound [1f] and the compound [21] is carried out in a suitable solvent. The solvent includes, for example, the solvents employed in the reaction of the R⁴ group-removed compound and the compound [6] in the above reaction scheme-I. The reaction is usually carried out at a temperature of from room temperature to 200° C., preferably from room temperature to 150° C., for 10 minutes to 5 hours. The compound [21] is usually used in an amount of at least 1 mole, preferably 1 to 10 moles, per 1 mole of the compound [1f]. ##STR25## wherein R^(2'), is as defined above, R^(3'), is a group ##STR26## (wherein R¹⁹ and R²⁰ are as defined above) or R³ (wherein R³ is as defined above), and R²⁴, R²⁵, R²⁶, R²⁷ are each a lower alkyl, and X⁹ is a halogen atom.

The reaction of the compound [37] and the compound [8] can be carried out under the same reaction condition as employed in the reaction of the compound [1b] and the compound [11] in the above reaction scheme-II.

The reaction of the compoud [29] and the compound [30a] or [30b] is carried out in the presence or absence of a solvent, preferably in the absence of any solvent. The solvent includes, for example, alcohols (e.g. methanol, ethanol, isopropanol, etc.), aromatic hydrocarbons (e.g. benzene, toluene, etc.), polar solvents (e.g. acetonitrile, DMF, DMSO, HMPA, etc.). The compound [30a] or [30b] is usually used in an amount of at least 1 mole, preferably 1 to 1.5 moles, per 1 mole of the compound [29]. The reaction is usually carried out at a temperature of from room temperature to 200° C., preferably from 60° to 200° C., for 0.5 to 25 hours.

The cyclization of the compound [31] or [32] can be carried out according to various known methods such as a heating method, a method using an acidic compound (e.g. phosphorus oxychloride, phosphorus pentachloride, phosphorus trichloride, thionyl chloride, conc. sulfuric acid, polyphosphoric acid, etc.). In case of using the heating method, the reaction is usually carried out in a high b.p. solvent such as a high b.p. hydrocarbon or a high b.p. ether (e.g. tetralin, diphenyl ether, diethylene glycol dimethyl ether, etc.) at a temperature of from 100° to 250° C., preferably from 150° to 200° C. In case of using the method using an acidic compound, the acidic compound is usually used in an equimolar to a large excess amount, preferably 10 to 20 moles, per 1 mole of the compound [31] or [32], and the reaction is usually carried out in the presence or absence of a suitable solvent at a temperature of from room temperature to 150° C. for 0.1 to 6 hours. The solvent includes acid anhydrides (e.g. acetic anhydride, etc.) in addition to the solvents employed in the cyclization of the above compound [9].

The hydrolysis of the compound [1i] can be carried out under the same reaction condition as employed in the hydrolysis of the compound [10] in the above reaction scheme-I.

The compound [1j] in which R^(3') is a group: ##STR27## can be coverted into the corresponding compound in which R^(3') is --CH₂ R¹⁹ by treating the former compound under the same reaction condition as employed in the reaciton wherein the compound [18] is converted into the compound [19] in the above reaction scheme-V.

The compound [29] employed as the starting material in the above reaciton scheme-IX can be prepared, for example, by the processes as shown in the following reaction schemes-X to XII. ##STR28## wherein R^(2'), R¹⁹, R²⁰, X⁶ and X⁹ are as defined above, and R²⁹ is a (lower) alkanoyl.

The desulfuration of the compound [16] or [29b] can be carried out under the same reaction conditions as employed in the desulfuration of the above compound [18].

The reaction of converting the compound [33] into the compound [34] is carried out in the presence of a (lower) alkanoylating agent such as a (lower) alkanoic acid (e.g. formic acid, acetic acid, propionic acid, etc.), a (lower) alkanoic acid anhydride (e.g. acetic anhydride, etc.), a (lower) alkanoic acid halide (e.g. acetyl chloride, propionyl bromide, etc.), or the like. In case of using an acid anhydride or an acid halide as the (lower) alkanoylating agent, a basic compound may be employed. The basic compound includes, for example, alkali metals (e.g. metallic sodium, metallic potassium, etc.), and hydroxides, carbonates or hydrogen carbonates thereof, organic bases (e.g. pyridine, piperidine, etc.), and the like. The reaction is carried out in the presence or absence of a solvent, usually in the presence of a suitable solvent. The solvent includes, for example, ketones (e.g. acetone, methyl ethyl ketone, etc.), ethers (e.g. diethyl ether, dioxane, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), acetic acid, acetic anhydride, water, pyridine, and the like. The (lower) alkanoylating agent is used in an amount of at least 1 mole per 1 mole of the compound [33], usually in equimolar to a large excess amount. The reaction is usually carried out at a temperature of from 0° to 150° C., preferably from 0° to 100° C., for 5 minutes to 10 hours. In case of using a (lower) alkanoic acid as the (lower) alkanoylating agent, a dehydrating agent is preferably employed. The dehydrating agent includes mineral acids (e.g. sulfuric acid, hydrochloric acid, etc.), sulfonic acids (e.g. p-toluenesulfonic acid, benzenesulfonic acid, ethanesulfonic acid, etc.), and the like. The reaction is preferably carried out at a temperature of from 50° to 120° C.

The nitration of the compound [33] or [34] is carried out by treating the said compound with a nitrating agent such as fuming nitric acid, conc. nitric acid, a mixed acid (e.g. nitric acid plus sulfuric acid, fuming sulfuric acid, phosphoric acid or acetic anhydride, etc.), an alkali metal nitrate plus sulfuric acid, an anhydride of nitric acid and an organic acid (e.g. acetyl nitrate, benzoyl nitrate, etc.), nitrogen tetraoxide, nitric acid plus mercury nitrate, nitrate of acetone cyanohydrin, an alkyl nitrate plus sulfuric acid or a polyphosphoric acid, or the like, in the presence or absence of a solvent such as acetic acid, acetic anhydride, sulfuric acid, or the like. The nitrating agent is preferably used in an amount of 1 to 1.5 moles per 1 mole of the compound [33] or [34]. The reaction is usually carried out at a temperature of from -10° to 70° C. for 1 to 24 hours.

The hydrolysis of the compound [35] is carried out under the same reaction conditions as employed in the hydrolysis of the above compound [10].

The reaction of the compound [37a] or [38] with the compound [8] can be carried out under the same reaction conditions as employed in the reaction of the compound [1b] and the compound [11] in the above reaction scheme-II.

The halogenation of the compound [39] can be carried out under the same reaction conditions as employed in the halogenation of the above compound [14].

The reaction of the compound [39a] and the compound [15] can be carried out under the same reaction conditions as employed in the reaction of the compound [14a] and the compound [15].

The convertion of the compound [29b] into the compound [29a] can be carried out under the same conditions as in the convertion of the compound [18] into the compound [19].

The reaction of converting the compound [36] into the compound [37] can be carried out by converting the former compound into a diazonium salt thereof using sodium nitrite and an acid (e.g. sulfuric acid, hydrochloric acid hydrobromic acid, boron fluoride, etc.) in a solvent such as a (lower) alkanoic acid (e.g. acetic acid), water, etc., and then reacting the diazonium salt with a copper powder or a copper halide (e.g. cuprous bromide, cuprous chloride, cupric chloride, etc.) in the presence of a hydrohalogenic acid (e.g. hydrobromic acid, hydrochloric acid, etc.), or with potassium iodide in the presence or absence of a copper powder, preferably with a copper halide in the presence of a hydrohalogenic acid. The sodium nitrite is usually used in an amount of 1 to 2 moles, preferably 1 to 1.5 moles, per 1 mole of the compound [36], and the copper halide is usually used in an amount of 1 to 5 moles, preferably 1 to 4 moles, per 1 mole of the compound. The reaction is usually carried out at a temprature of from -20° to 100° C., preferably form -5° to 100° C., for 10 minutes to 5 hours.

The halogen atom X⁹ in the compound [37a] can be converted into each other. ##STR29## wherein R^(2'), R¹⁹, R²⁰, R²⁹, X⁶ and X⁹ are as defined above.

The hydrolysis of the compound [40] can be carried out under the same reaction conditions as employed in the hydrolysis of the above compound [10].

The halogenation of the compound [41] can be carried out under the same reaction conditions as employed in the halogenation of the compound [14] in the above reaction scheme-V.

The reaction of the compound [42] and the compound can be carried out under the same reaction conditions as employed in the reaction of the compound [14a] and the compound [15].

The desulfuration of the compound [43] can be carried out under the same reaction conditions as employed in the desulfuration of the compound [18] in the above reaction scheme-V. ##STR30## wherein R^(2') and X⁹ are as defined above, A is a (lower) alkylene, m is 0 or 1, X¹⁰ is a halogen atom, or a phenylsulfonyloxy which may be substituted by a lower alkyl, and R³⁵ is hydrogen atom or nitro group.

The nitration of the compound [44] in the above reaction scheme-XII can be carried out under the same reaction conditions as employed in the nitration of the compound [34] in the above reaction scheme-X

The reaction of the compound [44] or [45] is usually carried out using a hydride reducing agent such as sodium borohydride, lithium aluminum hydride or diborane, and the reducing agent is usually used in an amount of at least 1 mole, preferably 1 to 3 moles, per 1 mole of the compound [44] or [45]. The reduction reaction is usually carried out in a suitable solvent, for example, water, (lower) alcohols (e.g. methanol, ethanol, isopropanol, etc.), ethers (e.g. tetrahydrofuran, diethyl ether, diglyme, etc.), DMSO, or the like, at a temperature of from -60° to 80° C., preferably from -30° C. to 50° C., for 10 minutes to 15 hours. In case of using lithium aluminum hydride or diborane as a reducing agent, an anhydrous solvent such as diethyl ether, tetrahydrofuran or diglyme is preferably employed.

The reaction of converting the compound [46] into the compound [47] wherein X¹⁰ is a halogen atom by halogenation is carried out under any reaction conditions usually employed in halogenation of hydroxy group, and may be carried out, for example, by reacting the compound [46] with a halogenating agent in the presence or absence of a suitable inert solvent. The halogenating agent includes, for example, hydrohalogenic acids (e.g. hydrochloric acid, hydrobromic acid, etc.), N,N-diethyl-1,2,2-trichlorovinylamide, phosphorus pentachloride, phosphorus pentabromide, phosphorus oxychloride, thionyl chloride, diethylaminosulfur trifluoride (DAST), and the like. The inert solvent includes, for example, ethers (e.g. dioxane, tetrahydrofuran, etc.), halogenated hydrocarbons (e.g. chloroform, dichloromethane, carbon tetrachloride, etc.), and the like. The halogenating agent is used in an amount of at least 1 mole per 1 mole of the compound [46], usually in an equimolar to an excess amount, the reaction is usually carried out at a temperature of from 0° to 150° C., preferably from 0° to 80° C., for 10 minutes to 15 hours. In case of using DAST as a halogenating agent, a basic compound such as triethylamine may be employed.

When the compound [46] is reacted with a phenylsulfonyl halide which may have a lower alkyl substituent on the phenyl ring, it may be converted into a compound [47] wherein X¹⁰ is a phenylsulfonyloxy which may be substituted with a lower alkyl. The reaction can be carried out in a suitable solvent in the presence of a basic compound.

The solvent includes, for example, ethers (e.g. diethyl ether, dioxane, tetrahydrofuran, monoglyme, diglyme, etc.), alcohols (e.g. methanol, ethanol, isopropanol, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), aliphatic hydrocarbons (e.g. n-hexane, heptane, cyclohexane, ligroin, etc.), amines (e.g. pyridine, N,N-dimethylaniline, etc.), halogenated hydrocarbons (e.g. chloroform, dichloromethane, carbon tetrachloride, etc.), aprotic polar solvents (e.g. DMF, DMSO, HMPA, etc.), and a mixture thereof. The basic compound includes inorganic bases (e.g. metallic sodium, metallic potassium, metallic magnesium, sodium hydride, sodium amide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, etc.), metal alcoholates (e.g. sodium methylate, sodium ethylate, etc.), organic bases (e.g. pyridine, piperidine, quinoline, triethylamine, N,N-dimethylaniline, etc.), and the like. The reaction is usually carried out at a temperature of from 0° to 120° C., preferably from room tempereture to 100 ° C., for 0.1 to 5 hours. The phenylsulfonyl halide which may have a lower alkyl substituent on the phenyl ring is usually used in an amount of at least 1 mole, preferably 1 to 3 moles, per 1 mole of the compound [46].

The compound [48] wherein R³⁵ is hydrogen atom is firstly converted into a compound [48] wherein R³⁵ is nitro by the same nitration reaction of the compound [44], and thereafter, it is reacted with the compound [8]. The reaction of the compound [48] thus converted and the compound [8] can be carried out under the same reaction conditions as employed in the reaction of the compound [1b] and the compound [11] in the above reaction scheme-II.

The reaction of ceonverting the compound [47] into the compound [48] can be carried out under the same reaction conditions as employed in the reduction of the above compound [45].

The compounds [46], [47] and [48] wherein R³⁵ is hydrogen atom can be converted into the corresponding compounds wherein R³⁵ is nitro by the same nitration reaction of the compound [44].

The compounds [44] and [45] can be prepared by the process as shown in the following reaction scheme. ##STR31## wherein R^(2'), R³⁵, X⁹, M and m are as defined above, and A' is a lower alkylene, provided that the groups (A')_(m) CH₂ -- and (A')_(m) CH₂ CH₂ -- have not more than 6 carbon atoms, R³⁶ is a lower alkyl, and X¹¹ is a halogen atom.

The reduction of the compound [55] is carried out under the same conditions as in the reduction of the compound [44] or [45]. Besides, the halogenation of the compound [56] can be carried out under the same conditions as in the halogenation of the compound [46].

The reaction of the compound [57] and the compound [58] is usually carried out in an appropriate solvent in the presence of a basic compound at a temperaure of from room temperature to 200° C., preferably from 60° to 120° C., for 1 to 24 hours. The solvent includes, for example, ethers (e.g. dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, diethyl ether, etc.), aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), lower alcohols (e.g. methanol, ethanol, isopropanol, etc.), polar solvents (e.g. dimethylformamide, dimethylsulfoxide, etc.), and the like. The basic compound includes, for example, inorganic bases (e.g. calcium carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium hydroxide, sodium amide, sodium hydride, potassium hydride, sodium methylate, sodium ethylate, etc.), amines (e.g. triethylamine, tripropylamine, pyridine, quinoline, etc.), and the like. The reaction proceeds favorably by using an alkali metal iodide (e.g. potassium iodide, sodium iodide, etc.). The compound [58]is usually used in an equimolar to excess amount, preferably 1 to 5 moles, more preferably 1 to 1.2 mole, per 1 mole of the compound [57].

The reaction of the compound [57] and the compound [17] can be carried out under the same conditions as in the reaction of the compound [16] and the compound [17]. Besides, the hydrolysis of the compound [59] or [60] can be carried out under the same conditions as in the hydrolysis of the compound [20].

The compounds [10] in the reaction scheme-I and the compounds [1b] and [1b'] in the reaction scheme-II are useful not only as an intermediate for preparing the present compounds [1] having antimicrobial activities, but also as an antimicrobial agent because they also have antimicrobial activities.

In the compounds of the present invention there are optical and geometrical isomers, and the present invention includes also these isomers.

Among the present compounds [1], the preferable ones are the compounds wherein R³ is methyl or ethyl (in particular, methyl).

The compounds [1] can easily be converted into a salt thereof by treaing them with a pharmaceutically acceptable acid or base. The acid includes inorganic acids (e.g. hydrochloric acid, sulfuric acid, phosphoric acid, hydrobromic acid, etc.) and organic acids (e.g. oxalic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid, lactic acid, benzoic acid, methanesulfonic acid, propionic acid, etc.). The base includes sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carboante, potasium hydrogen carbonate, and the like.

The compound thus obtained can easily be isolated by conventional methods, such as extraction with solvents, dilution method, recrystallization, column chromatography, preparative thin layer chromatography, and the like.

The compounds [1] of the present invention or salts thereof show excellent antimicrobial activity against Pseudomonas aeruginosa, anaerobic bacteria, resistant cells against various antimicrobials, clinically isolated bacteria, and gram negative and gram positive bacteria (e.g. Enterococcus faecalis, Staphylococcus pyogenes, etc.), and hence, are useful as an antimicrobial agent for the treatment of diseases induced by these microorganisms. These compounds show also low toxicity and less side effect and are characteristic in good absorbability and in sustained activity. Moreover, the compounds are highly excreted via urine and hence are useful for the treatment of urinary infectious diseases, and further because of easy excretion via bile, they are also useful for the treatment of intestinal infectious diseases Besides, the compounds of this invention show improved absorbability into body by using them in the form of a salt such as lactate, hydrochloride, etc.

The compounds of the present invention are usually used in the form of a usual pharmaceutical preparation. The pharmaceutical preparation can be prepared in admixture with conventional pharmaceutically acceptable diluents or carriers, such as fillers, weighting agents, binding agents, wetting agents, disintegrators, surfactants, lubricating agents, and the like. The pharmaceutical preparation includes various preparations suitable for treatment of the diseases, for example, tablets, pills, powders, solutions, suspensions, emulsions, granules, capsules, suppositories, injections (solutions, suspensions, etc.), and the like. In the preparation of tablets, there may be used any conventional carriers, for example, excepients (e.g. lactose, white sugar, sodium chloride, glucose, urea, starches, calcium carbonate, kaolin, crystalline cellulose, silicate, etc.), binding agents (e.g. water, ethanol, propanol, simple syrup, glucose solution, starch solution, gelatin solution, carboxymethyl cellulose, shellac, methyl cellulose, potassium phosphate, polyvinylpyrrolidone, etc.), disintegrators (e.g. dry starch, sodium alginate, agar powder, laminaran powder, sodium hydrogen carbonate, calcium carbonate, polyoxyethylene sorbitan fatty acid esters, sodium laurylsulfate, stearic monoglyceride, starches, lactose, etc.), disintegration inhibitors (e.g. white sugar, stearin, cacao butter, hydrogenated oils, etc.), absorption promoters (e.g. quaternary ammonium salts, sodium laurylsulfate, etc.), wetting agents (e.g. glycerin, starches, etc.), adsorbents (e.g. starches, lactose, kaolin, bentonite, colloidal silicates, etc.), rublicants (e.g. purified talc, stearates, boric acid powder, polyethylene glycol, etc.), and the like. The tablets may also be coated with conventional coating agents, for example, may be in the form of a sugar coated tablet, a gelatin-coated tablets, an enteric coating tablet, a film coating tablet, or a double or multiple layers tablet. In the preparation of pills, there may be used conventional carries, such as excipients (e.g. glucose, lactose, starches, cacao butter, hydrogenated vegetable oils, kaolin, talc, etc.), binding agents (e.g. gum arabic powder, tragacanth powder, gelatin, ethanol, etc.), disintegrators (e.g. laminaran, agar, etc.), and the like. In the preparation of suppositories, there may be used conventional carriers, such as polyethylene glycol, cacao butter, higher alcohols, higher alcohol esters, gelatin, semi-synthetized glycerides, and the like. In the preparation of injections, the solutions, emulsions or suspensions of the compounds are sterilized and are preferably made isotonic with the body liquid. These solutions, emulsions and suspensions are prepared by admixing the active compound with a conventional diluent, such as water, aqueous lactic acid solution, ethyl alcohol, propylene glycol, ethoxylated isostearyl alcohol, polyoxylated isostearyl alcohol, polyoxyethylene sorbitan fatty acid esters, and the like. The preparations may also be incorporated with sodium chloride, glucose or glycerin in an amount sufficient to make them isotonic with the body liquid. The preparations may also be incorported with conventional solubilizers, buffering agents, anesthetizing agents, and further, with coloring agents, preservatives, perfumes, flavors, sweeting agents, and other medicaments. The preparations in the form of a paste, cream or gel may be prepared by using as a diluent white vaseline, paraffin, glycerin, cellulose derivatives, polyethylene glycol, silicone, bentonite, or the like.

The pharmaceutical preparation of the present invention may also be in the form of an infusable or injectable solution containing the above compound [1] or a salt thereof (e.g. lactate, etc.), and an acid not producing a precipitate. The acid not producing a precipitate includes, for example, lactic acid, methanesulfonic acid, propionic acid, hydrochloric acid, succinic acid, and the like, preferably lactic acid. In case of using lactic acid, the acid is usually used in an amount of from 0.1 to 10% by weight, preferably from 0.5 to 2% by weight, based on the weight of the above infusable or injectable solution. In case of using an acid other than lactic acid, the acid is usually used in an amount of from 0.05 to 4% by weight, preferably from 0.3 to 2% by weight, based on the weight of the above solution. Moreover, a conventional additive may optionally be added to the above infusable or injectable solution. The additive includes, for example, a thickener, an absorption promoter or inhibitor, a crystallization inhibitor, a complex-forming agent, an antioxidant, an isotonicity-giving agent, or a hydrating agent, and the like. The pH of the solution can properly be adjusted by adding an alkali such as sodium hydroxide, and is usually adjusted within the range of from 2.5 to 7. The infusable or injectable solution thus prepared has an excellent stability, and can be stored and preserved for a long time with retaining the solution state.

The active compounds [1] or salts thereof may be contained in any amount in the preparations, and are usually contained in an amount of 1 to 70% by weight based on the whole weight of the preparations.

The pharmaceutical preparations of the present invention can be administered in any methods. Suitable method for administration may be selected in accordance with the preparation form, age and sex of the patients, degree of severity of the diseases, and the like. For instance, tablets, pills, solutions, suspensions, emulsions, granules and capsules are administered in oral route. In case of injection, it is administered intravenously alone or together with an auxiliary liquid (e.g. glucose, amino acid solution, etc.). The injections may also be administered in intramuscular, intracutaneous, subcutaneous, or intraperitoneal route. Suppositories are administered in intrarectal route.

The dosage of the pharmaceutical preparations of the present invention may vary according to administration methods, age and sex of the patients, severity of the diseases, and the like, but is usually in the range of about 0.2 to 100 mg of the active compound [1] or a salt thereof per 1 kg of body weight of the patient per day. The preparation is usually administered by dividing into 2 to 4 times per day.

The present invention is illustrated by the following Reference Examples, Examples, and Experiments.

REFERENCE EXAMPLE 1

To a solution of 2-bromo-4,5-difluoroaniline (100 g) and dimethyl sulfide (49 ml) in anhydrous dichloromethane (1.2 liter) is added gradually N-chlorosuccinimide (90 g) at below 15° C., and thereafter is further added in portions triethylamine (93 ml) at 15° C. After the addition, the mixture is refluxed for 7 hours. After cooling, 10% aqueous sodium hydroxide (one liter) is added to the reaction mixture, and the mixture is extracted with dichloromethane. The extract is dried over magnesium sulfate and concentrated, and the resulting residue is purified by silica gel column chromatography (solvent, dichloromethane:n-hexane=1:2). The product is recrystallized from n-hexane to give 6-bromo-3,4-difluoro-2-methylthiomethylaniline (52 g) as a white crystal, m.p. 60°-61° C.

REFERENCE EXAMPLE 2

A mixture of 6-bromo-3,4-difluoro-2-methylthiomethylaniline (99 g), HMPA (130 g) and copper cyanide (48 g) is heated at 150° C. for 4 hours. After cooling, the reaction mixture is poured into a solution of ethylenediamine (50 ml) in water (500 ml), and the mixture is heated at 60° C. for one hour. After cooling, the mixture is extracted with ethyl acetate, and the extract is dried over magnesium sulfate and concentrated. The resulting residue is purified by silica gel column chromatography (solvent, dichloromethane:n-hexane=1:1), and the product is recrystallized from ethanol to give 2-amino-4,5-difluoro-3-methylthiomethylbenzonitrile (28 g), as a white crystal, m.p. 109°-110° C.

REFERENCE EXAMPLE 3

To a solution of 2-amino-4,5-difluoro-3-methylthiomethylbenzonitrile (4.0 g) in ethanol (80 ml) are added Raney nickel (40 ml) with ethanol (80 ml). The mixture is stirred at 40°-50° C. for 30 minutes, and then filterd. To the filtrate is added water, the reaction mixture is extracted with ethyl acetate. The extract is dried over magnesium sulfate and concentrated. The product is recrystallized from n-hexane to give 2-amino-4,5-difluoro-3-methylbenzonitrile (2.4 g), as a white crystal, m.p. 114°-116° C.

REFERENCE EXAMPLE 4

Sodium nitrite (5.6 g) is added to conc. sulfuric acid (59 ml) at below 70° C. The mixture is heated at 70° C. for 10 minutes and then cooled, and thereto is added dropwise a solution of 2-amino-4,5-difluoro-3-methylbenzonitrile (12.3 g) in acetic acid (123 ml) at below 40° C. The mixture is stirred at the same temperature for 30 minutes and then added in portions to a solution of cuprous chloride (20 g) in conc. hydrochloric acid (200 ml), and thereafter is heated at 80° C. for 30 minutes. After cooling, to the reaction mixture is added ice water, and ethyl acetate is distilled off. The resulting residue is purified by silica gel column chromatography (solvent, dichloromethane:n-hexane =1:1) to give 2-chloro-4,5-difluoro-3-methylbenzonitrile (8.0 g), as a white crystal, m.p. 59°-61° C.

REFERENCE EXAMPLE 5

To 2-chloro-4,5-difluoro-3-methylbenzonitrile (4.0 g) is added 60% sulfuric acid (20 ml), and the mixture is heated at 140°-150° C. for 3 hours. After cooling, the reaction mixture is poured into ice water, and the mixture is extracted with dichloromethane. The extract is dried over magnesium sulfate and the solvent is distilled off. To the residue is added n-hexane, and the precipitate is separated by filtration to give 2-chloro-4,5-difluoro-3-methylbenzoic acid (3.1 g), as a white crystal, m.p. 121°-122° C.

REFERENCE EXAMPLE 6

To 2-chloro-4,5-difluoro-3-methylbenzoic acid (3.1 g) is added thionyl chloride (6 ml), and the mixture is reflexed for one hour. The mixture is concentrated under reduced pressure to give 2-chloro-4,5-difluoro-3-methylbenzoyl chloride (3.3 g).

Separately, metallic magnesium (0.38 g) is suspended in anhydrous ethanol (0.8 ml) and thereto is added a few drops of carbon tetrachloride. When the reaction is started, a mixture of diethyl malonate (2.3 ml), anhydorus ethanol (1.5 ml) and anhydrous toluene (6 ml) is added portionwise at 50°-60° C. Thereto is added dropwise a solution of the above 2-chloro-4,5-difluoro-3-methylbenzoyl chloride (3.3 g) in anhydrous toluene (5 ml) at 0° C. After the addition, the mixture is stirred at room temperature for 30 minutes. To the raction mixture is added a mixture of conc. sulfuric acid (0.4 ml) and water (8 ml) and the mixture is extracted with diethyl ether. The extract is dried over magnesium sulfate and the solvent is then distilled off to give diethyl 2-chloro-3-methyl-4,5-difluorobenzoylmalonate (5.1 g).

REFERENCE EXAMPLE 7

To diethyl 2-chloro-3-methyl-4,5-difluorobenzoylmalonate (5.1 g) are added water (10 ml) and p-toluenesulfonic acid (30 ml), and the mixture is refluxed for 4 hours. After cooling, the mixture is extracted with diethyl ether and the extract is dried over magnesium sulfuate. The diethyl ether is distileld off to give ethyl 2-chloro-4,5-difluoro- 3-methylbenzoyl acetate (3.9 g).

REFERENCE EXAMPLE 8

To ethyl 2-chloro-4,5-difluoro-3-methylbenzoylacetate (3.9 g) are added triethoxymethane (3.1 g) and acetic anhydride (3.4 g), and the mixture is heated at 150° C. for one hour. The mixture is concentrated to give ethyl 2-(2-chloro-3-methyl-4,5-difluorobenzoyl)-3-ethoxyacrylate. To the product is added ethanol (50 ml) and thereto is added cyclopropylamine (1.1 ml) at room temperture, and the mixture is stirred for 30 minutes. Ethanol is distilled off to give ethyl 2-(2-chloro-3-methyl-4,5-difluorobenzoyl)-3-cyclopropylaminoacrylate. To the product is added anhydrous dioxane (30 ml) and thereto is added portionwise 60% sodium hydride (0.6 g). The mixture is stirred at room temperature for 30 minutes and then refluxed for one hour. The reaction mixture is poured into aquoeus saturated ammonium chloride and extracted with dichloromethane. The extract is dried over magnesium sulfate and concentrated to give ethyl 1-cyclopropyl-6,7-difluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate (2.2 g).

NMR (CDCl₃) δ: 8.64 (1H, s), 8.10 (1H, t, J=10 Hz), 4.36 (2H, q, J=7.5 Hz), 3.76-4.10 (1H, m), 2.76 (3H, d, J=4.5 Hz), 1.37 (3H, t, J=7.5 Hz , 0.86-1.30 (4H, m).

REFERENCE EXAMPLE 9

To ethyl 1-cyclopropyl-6,7-difluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate (2.2 g) are added conc. hydrochloric acid (5 ml), water (2 ml) and acetic acid (20 ml), and the mixture is refluxed for 2 hours. After cooling, the precipitated crystals are separated by filtration, and washed with water, ethanol and diethyl ether in this order to give 1-cyclopropyl-6,7-difluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (1.8 g) as a white crystal, m.p. 240°-243° C.

REFERENCE EXAMPLE 10

To 1-cyclopropyl-6,7-difluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (1.0 g) are added triacetylborone [B(OCOCH₃)₃ ] (1.0 g) and acetic anhydride (10 ml) and the mixture is heated at 140° C. for 15 minutes. After the reaction, the mixture is concentrated and to the resulting residue is added diethyl ether and the crystals are separated by filtration to give 6,7-difluoro-1-cyclopropyl-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid--B(OCOCH₃)₂ chelate (1.2 g).

NMR (CDCl₃) δ: 9.32 (1H, s), 8.23 (1H, t, J=9 Hz), 4.30-4.58 (1H, m), 2.97 (3H, d, J=3 Hz), 2.03 (6H, s), 1.13-1.60 (4H, m).

REFERENCE EXAMPLE 16

Into a solution of 6-bromo-3,4-difluoro-2-methylthiomethylaniline (6.00 g) in ethanol (120 ml) is suspensed Raney nickel (70 ml), and the mixture is stirred at 50° C. for 30 minutes. After removing Raney nickel by filtration, the filtrate is concentrated to give 3,4-difluoro-2-methylaniline (3.77 g) as a colorless oil.

NMR (CDCl₃) δ: 6.72 (1H, ddd, J=10.2 Hz, 10.2 Hz, 8.7 Hz), 6.27 (1H, ddd, J=10.2 Hz, 6.0 Hz, 2.7 Hz), 3.43 (2H, br), 2.02 (3H, d, J=2.4 Hz).

REFERENCE EXAMPLE 17

To 3,4-difluoro-2-methylaniline (3.27 g) is added acetic anhydride (50 ml), and the mixture is stirred for 10 minutes. After distilling off acetic anhydride, the resulting residue is extracted with dichloromethane. The extract is washed with water, aqueous saturated sodium hydrogen carbonate and aqueous saturated sodium chloride in this order, and then dried over anhydrous magnesium sulfate. After distilling off dichloromethane, the residue is recrystallized from ethyl acetate--n-hexane to give 3,4-difluoro-2-methylacetaniline (3.86 g) as colorless needles, m.p. 145.5°-146.0° C.

REFERENCE EXAMPLE 18

3,4-Difluoro-2-methylacetanilide (100 mg) is added to ice-cooled conc. sulfuric acid (b 0.3 ml) and thereto is added conc. nitric acid (0.1 ml) under ice cooling, and the mixture is stirred at room temperature for 2 hours. To the mixture is further added conc. nitric acid (0.1 ml), and the mixture is stirred at room temperature overnight. To the reaction mixture is added a large amount of water, and the mixture is extracted with dichloromethane. The extract is washed with water, aqueous saturated sodium hydrogen carbonate and aqueous saturated sodium chloride in this order and then dired over anhydrous magnesium sulfate. After distilling off dichloromethane, the residue is recrystallized from ethyl acetate--n-hexane to give 4,5-difluoro-6-methyl-2-nitroacetanilide (80.7 mg) as yellow needles, m.p. 152.1°-152.6° C.

REFERENCE EXAMPLE 19

4,5-Difluoro-6-methyl-2-nitroacetanilide (81 mg) is dissolved in acetic acid (2 ml) and thereto is added conc. hydrochloric acid (1 ml) at 0° C. The mixture is stirred at 100° C. overnight and then concentrated. The residue is neutralized with aqueous saturated sodium hydrogen carbonate and extracted with dichloromethane. The extract is washed with aqueous saturated sodium chloride and dried over anhydrous magnesium sulfate. Dichloromethane is distilled off to give 4,5-difluoro-6-methyl-2-nitroaniline (59 mg) as orange prisms, m.p. 87.2°-88.0° C.

REFERENCE EXAMPLE 20

Sodium nitrite (30 mg) is added portionwise to conc. hydrochloric acid (0.32 ml), and the mixture is stirred at 70° C. for 10 minutes and cooled to room temperature and thereto is added dropwise a solution of 4,5-difluoro-6-methyl-2-nitroanline (59 mg) in acetic acid (6.5 ml) at the same temperature. The mixture is stirred at room temperature for 30 mintues and thereto is added dropwise a solution of cuprous chloride (107 mg) in conc. hydrochloric acid (1.0 ml). The mixture is stirred at 80° C. for 30 minutes. To the reaction mixture is added water and the mixture is extracted with ethyl acetate. The extract is washed with water, aqueous saturated sodium hydrogen caronate and aqueous saturated sodium chloride in this order and then dried over anhydrous magnesium sulfate. Ethyl acetate is distilled off to give 2-chloro-5,6-difluoro-3-nitrotoluene (54 mg).

NMR (CDCl₃) δ: 7.58 (1H, dd, J=11.0 Hz, 8.0 Hz), 2.40 (3H, s).

REFERENCE EXAMPLE 23

To a solution of 3,4-difluoroacetanilide (85.5 g) in sulfuric acid (850 ml) is added gradually with stirring potassium nitrate (55.5 g) at room temperature during which the temperature raises to 60° C. The mixture is stirred at 60° C. for one hour. The reaction mixture is poured into ice water, and the precipitated crystals are taken by filtration. The precipitates are dissolved in dichloromethane and washed with aqueous sodium hydrogen carbonate, water and aqueous saturated sodium chloride in this order and dried. The solvent is removed by concentration and washed with n-hexane. The resulting crystals are taken by filtration and dried to give 2-nitro-4,5-difluoroaniline (54 g).

NMR (CDCl₃) δ: 5.76-6.40 (2H, m), 6.60 (1H, dd, J=12 Hz, 7 Hz), 7.97 (1H, dd, J=10.5 Hz, 8.5 Hz)

REFERENCE EXAMPLE 24

To a solution of 2-nitro-4,5-difluoroaniline (1.0 g) and dimethylsulfide (1.79 g) in dichloromethane (40 ml) is added gradually N-chlorosuccinimide (3.82 g) with stirring at below 15° C. The mixture is stirred for 30 minutes, and thereto is added triethylamine (2.89 g), and the mixture is refluxed for 21 hours. After allowing to cool, the reaction mixture is washed with 10% aqueous sodium hydroxide, water and aqueous sodium chloride in this order and dried. The solvent is removed by concentration, and the resulting residue is purified by silica gel column chromatography (solvent, n-hexane:ethyl acetate=30:1) and then recrystallized from n-hexane to give 2-nitro-4,5-difluoro-6-methylthiomethylaniline (0.47 g) as yellow needles, m.p. 110°-111.5° C.

REFERENCE EXAMPLE 25

Sodium nitrite (0.15 g) is added to conc. sulfuric acid (15 ml) and the mixture is stirred at 70° C. for 10 minutes. To the mixture is added dropwise a solution of 2-nitro-4,5-difluoro-6-methylthiomethylaniline (0.45 g) in acetic acid (4.5 ml). The mixture is stirred at the same temperature for 45 minutes, and thereto is further added dropwise a solution of cuprous chloride (0.52 g) in conc. hydrochloric acid (5.2 ml). The mixture is stirred at 80° C. for 1.5 hour, and the reaction mixture is poured into ice water and extracted with ethyl acetate. The extract is washed with water and aqueous saturated sodium chloride in this order and dried, and then the solvent is disilled off. The resulting residue is purified by silica gel column chromatography (solvent, n-hexane:ethyl acetate=30:1) to give 2-chloro-3-methylthio-4,5-difluoro-1-nitrobenzene (0.16 g).

NMR (CDCl₃) δ: 2.15 (3H, s), 3.92 (2H, dd, J=3 Hz), 7.67 (1H, dd, J=8.5 Hz, 8 Hz)

REFERENCE EXAMPLE 26

2,3,6-Trifluorobenzoic acid (21.0 g) is added to conc. sulfuric acid (120 ml) under ice-cooling. To the mixture is added dropwise a solution of potassium nitrate (14.5 g) in conc sulfuric acid (30 ml) at below 20° C. After the addition, the mixture is stirred at room temperature for one hour. The reaction mixture is poured into ice water and extracted with diethyl ether. The extract is dried over magnesium sulfate, and then the solvent is distilled off. The residue is recrystallized from dichloromethane--n-hexane to give 2,5,6-trifluoro-3-nitrobenzoic acid (22 g), as colorless prisms, m.p. 98°-99° C.

NMR (CDCl₃) δ: 8.11-8.23 (1H, m), 9.10 (1H, brs)

REFERENCE EXAMPLE 27

To a solution of sodium boron hydroxide (44 g) in anhydrous tetrahydrofuran is added a solution of 2,5,6-trifluoro-3-nitrobenzoic acid (22 g) in anhydrous tetrahydrofuran (40 ml) at below 10° C., and thereto is further added dropwise a solution of boron trifluoride etherate (20 ml) in anhydrous tetrahydrofuran (40 ml) at below 10° C. After the addition, the mixture is stirred at room temperature for one hour. The reaction mixture is poured into ice water and extracted with diethyl ether. The extract is dried, and then the solvent is distilled off to give 2,5,6-trifluoro-3-nitrobenzyl alcohol (14 g).

NMR (CDCl₃) δ: 2.56 (1H, brs), 4.88 (2H, t, J=1.8 Hz), 7.92-8.04 (1H, m)

REFERENCE EXAMPLE 28

To a solution of 2,5,6-trifluoro-3-nitrobenzyl alcohol (14 g) in ethanol (64 ml) and water (7 ml) is added a mixture of 4-ethoxycarbonylpiperazine (11 g), triethylamine (12.5 g) and ethanol (18 ml) at one time. The mixture is stirred at room temperature overnight, and the resulting precipitates are separated by filtration. The crystals are washed with a small amount of diethyl ether and recrystallized from ethanol to give 3,6-difluoro-2-(4-ethoxycarbonyl-1-piperazinyl)-5-nitrobenzyl alcohol (8.7 g), as yellow needles, m.p. 147°-149° C.

REFERENCE EXAMPLE 29

To a solution of 3,6-difluoro-2-(4-ethoxycarbonyl-1-piperazinyl)-5-nitrobenzyl alcohol (8.5 g) in chloroform (85 ml) is added thionyl chloride (2.7 ml) at room temperature. The mixture is stirred at the same temperature for 30 mintues, and the reaction mixture is poured into ice water, and then neutralize with sodium hydrogen carbonate and extracted with diethyl ether. The extract is dried over magnesium sulfate, and then the solvent is distilled off to give 2-(4-ethoxycarbonyl-1-piperazinyl)-3,6-difluoro-5-nitrobenzyl chloride (8.1 g).

NMR (CDCl₃) δ: 1.28 (3H, t, J=7.1 Hz), 3.08-3.33 (4H, m), 3.46-3.75 (4H, m), 4.18 (2H, q, J=7.1 Hz), 4.77 (2H, d, J=2.5 Hz), 7.82 (1H, dd, J=9.2 Hz, 7.2 Hz)

REFERENCE EXAMPLE 30

To a solution of 3,6-difluoro-2-(4-ethoxycarbonyl-1-piperazinyl)-5-nitrobenzyl chloride (8.1 g) in dimethylsulfoxide (90 ml) is added gradually sodium boron hydride (1.8 g) at below 30° C. The mixture is stirred at the same temperature for one hour, and the reaction mixture is pored into ice water, and then acidified with conc. hydrochloric acid and extracted with diethyl ether. The solvent is distilled off to give 2-(4-ethoxycarbonyl-1-piperazinyl)-3,6-difluoro-5-nitrotoluene (7.1 g).

NMR (CDCl₃) δ: 1.26 (3H, t, J=7.1 Hz), 2.30 (3H, d, J=3 Hz), 2.76-3.27 (5H, m), 3.50-3.75 (4H, m), 4.17 (2H, q, J=7.1 Hz), 7.60 (1H, dd, J=9.3 Hz, 7.2 Hz)

REFERENCE EXAMPLE 31

To 3,6-difluoro-2-(4-ethoxycarbonyl-1-piperazinyl)-5-nitrotoluene (7.1 g) are added anhydrous dimethylsulfoxide (23 ml), potassium fluoride (2.0 g) and cyclopropylamine (1.5 g), and the mixture is heated at 60° C. for 6 hours. The reaction mixture is poured into ice water, and extracted with dichloromethane. The solvent is distilled off and the residue is recrystallized from ethanol to give N-cyclopropyl-2-methyl-3-(4-ethoxycarbonyl-1-piperazinyl)-4-fluoro-6-nitroaniline (7.4 g), as orange red prisms, m.p. 97°-98° C.

NMR (CDCl₃) δ: 0.50-0.54 (2H, m), 0.66-0.74 (2H, m), 1.28 (3H, t, J=7.1 Hz), 2.43 (3H, s), 2.63-2.90 (1H, m), 3.07-3.28 (4H, m), 3.47-3.77 (4H, m), 4.20 (2H, q, J=7.1 Hz), 7.53 (1H, brs), 7.70 (1H, dd, J=13 Hz)

REFERENCE EXAMPLE 32

To N-cyclopropyl-2-methyl-3-(4-ethoxycarbonyl-1-piperazinyl)-4-fluoro-6-nitroaniline (7.1 g) is added diethyl ethoxymethylenemalonate (4.6 g), and the mixture is reacted at 150°-170° C. for 17 hours. After cooling, the solvent is distilled off, and the resulting residue is subjected to silica gel column chromatography (solvent, dichloromethane:n-hexane=2:1 dichloromethane) to give diethyl [N-cyclopropyl-N-[3-(4-ethoxycarbonyl-1-piperazinyl)-2-methyl-4-fluoro-6-nitrophenyl]aminomethylene]malonate (5.4 g).

REFERENCE EXAMPLE 33

To a solution of diethyl [N-cyclopropyl-N-[3-(4-ethoxycarbonyl-1-piperazinyl)-2-methyl-4-fluoro-6-nitrophenyl]aminomethylene]malonate (1.0 g) in acetic anhydride (5 ml) is added conc. sulfuric acid (2 ml) with keeping at 50°-70° C. After stirring for 30 minutes, the reaction mixture is poured into ice water, and neutralized with potassium carbonate. The mixture is extracted with ethyl acetate, and the solvent is distilled off, and the resulting residue is purified by silica gel column chromatography (solvent, dichloromethane:methanol=10:1) and then recrystallized from ethyl acetate to give ethyl 1-cyclopropyl-7-(4-ethoxycarbonyl-1-piperazinyl)-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate (0.19 g), as colorless prisms, m.p. 200°-202° C.

In the same manner as described in Reference Example 33 by using appropriate starting materials, there are prepared the same compounds as in Reference Examples 8, 15 and 13.

REFERENCE EXAMPLES 34

In the same manner as described in Reference Example 28 by using appropriate starting material, there is prepared the following compound:

3,6-Difluoro-2-(4-benzyl-3-methyl-1-piperazinyl)-5-nitrobenzyl alcohol

NMR (CDCl₃) δ: 1.18 (3H, d, J=6 Hz), 2.20-2.38 (1H, m), 2.55-2.72 (1H, m), 2.72-2.91 (1H, m), 3.06-3.44 (5H, m), 4.09 (1H, d, J=13 Hz), 4.77 (2H, br), 7.12-7.40 (5H, m), 7.71 (1H, dd, J=9.5 Hz, 7.2 Hz)

REFERENCE EXAMPLES 35

In the same manner as described in Reference Example 29 by using appropriate starting material, there is prepared the following compound:

2-(4-Benzyl-3-methyl-1-piperazinyl)-3,6-difluoro-5-nitrobenzyl chloride

NMR (CDCl₃) δ: 1.21 (3H, d, J=6 Hz), 2.24-2.50 (1H, m), 2.60-3.00 (2H, m), 3.00-3.46 (5H, m), 4.11 (1H, d, J=13 Hz), 4.75 (2H, brs), 7.26-7.45 (5H, m), 7.79 (1H, dd, J=9.5 Hz, 7.3 Hz)

REFERENCE EXAMPLES 36

In the same manner as described in Reference Example 30 by using appropriate starting material, there is prepared the following compound:

2-(4-Benzyl-3-methyl-1-piperazinyl)-3,6-difluoro-5-nitrotoluene

NMR (CDCl₃) δ: 1.18 (3H, d, J=6 Hz), 2.25 (3H, d, J=3.3 Hz), 2.30-2.48 (1H, m), 2.50-3.38 (7H, m), 4.08 (1H, d, J=13 Hz), 7.15-7.46 (5H, m), 7.58 (1H, dd, J=7.5 Hz, 9.5 Hz)

REFERENCE EXAMPLES 37

In the same manner as described in Reference Example 31 by using appropriate starting material, there is prepared the following compound:

N-Cyclopropyl-2-methyl-3-(4-benzyl-3-methyl-1-piperazinyl)-4-fluoro-6-nitroaniline

NMR (CDCl₃) δ: 0.52-0.68 (2H, m), 0.70-0.87 (2H, m), 1.28 (3H, d, J=6 Hz), 2.22-2.40 (1H, m), 2.38 (3H, s), 2.58-3.37 (8H, m), 7.26-7.44 (5H, m), 7.60 (1H, brs), 4.11 (1H, d, J=13 Hz), 7.77 (1H, dd, J=13.2 Hz)

REFERENCE EXAMPLES 38

In the same manner as described in Reference Examples 32 and 33 by using appropriate starting material, there is prepared the following compound:

Ethyl 1-cyclopropyl-7-(4-benzyl-3-methyl-1-piperazinyl)-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate, m.p. 172°-173° C., white powder (recrystallized from ethyl acetate)

REFERENCE EXAMPLE 66

To 2-chloro-5,6-difluoro-3-nitrotoluene (1.0 g) are added spray-dried potassium fluoride (1.4 g), anhydrous dimethylsulfoxide (10 ml) and benzene (10 ml), and the moisture is removed by azeotropic distillation together with benzene. Subsequently, the mixture is stirred at 170°-180° C. under argon stream for 3.5 hours. After cooling, the reaction mixture is poured into ice water and extracted with diethyl ether. The extract is washed with water, dried and then the solvent is distilled off. The residue is purified by silica gel column chromatography (solvent, n-hexane) to give 2,5,6-trifluoro-3-nitrotoluene (0.45 g).

NMR (CDCl₃) δ: 2.34-2.37 (3H, m), 7.75-8.00 (1H, m)

REFERENCE EXAMPLE 69

To a solution of sodium boron hydride (51.6 g) in tetrahydrofuran (500 ml) is added dropwise a solution of 2,5,6-trifluorobenzoic acid (120 g) in tetrahydrofuran (200 ml) with stirring at below 10° C., and thereto is further added dropwise a solution of BF₃.(C₂ H₅)₂ O (232 ml) in tetrahydrofuran (500 ml) under ice cooling. The mixture is stirred at room temperature overnight. The reaction mixture is poured into ice water (1.5 liter) and is extracted with diethyl ether. The extract is dried over magnesium sulfate and the solvent is distilled off under reduced pressure to give 2,3,6-trifluorobenzyl alcohol (112.7 g), as pale yellow oil, b.p. 112° C. (30 mmHg).

REFERENCE EXAMPLE 70

To a solution of 2,3,6-trifluorobenzyl alcohol (41 g) in dichloromethane (100 ml) is added dropwise a solution of thionyl chloride (50 ml) in dichloromethane (80 ml) under ice cooling with stirring, and the mixture is stirred at room temperature overnitht. To the mixture is added triethylamine (10 ml), and the solvent is distilled off under reduced pressure to give 2,3,6-trifluorobenzyl chloride (28.6 g), as colorless oil, b.p. 63° C. (13 mmHg).

NMR (CDCl₃) δ: 4.66 (2H, s), 6.62-6.93 (1H, m), 7.04-7.26 (1H, m)

REFERENCE EXAMPLE 71

To a solution of sodium cyanide (1.94 g) in water (4 ml) is added phenyltriethylammonium chloride (0.09 g), and thereto is added with stirring 2,3,6-trifluorobenzyl chloride (5.0 g), and the mixture is stirred at 90° to 100° C. for 40 minutes. The reaction mixture is poured into water (20 ml) and is extracted with diethyl ether. The extract is dried over potassium carbonate and the solvent is distilled off to give 2-(2,3,6-trifluorophenyl)acetonitrile (3.1 g), b.p. 80°-85° C. (5 mmHg).

NMR (CDCl₃) δ: 3.76 (2H, d, J=0.8 Hz), 6.89-6.98 (1H, m), 7.11-7.26 (1H, m)

REFERENCE EXAMPLE 72

2-(2,3,6-Trifluorophenyl)acetonitrile (13.3 g) is dissolved in ethanol (20 ml), and thereto is carefully added conc. sulfuric acid (8.5 ml), and the mixture is refluxed at 125° C. for 7 hours. After cooling, the reaction mixture is fractionated with diethyl ether and water. The ether layer is washed with aqueous saturated sodium chloride and dried over magnesium sulfate and then concentrated under reduced pressure to give ethyl 2-(2,3,6-trifluorophenyl)acetate (16.3 g), as colorless oil.

NMR (CDCl₃) δ: 1.27 (3H, t, J=7.1 Hz), 3.72 (2H, d, J=1.2 Hz), 4.19 (2H, q, J=7.1 Hz), 6.78-6.90 (1H, m), 7.00-7.16 (1H, m)

REFERENCE EXAMPLE 73

Ethyl 2-(2,3,6-trifluorophenyl)acetate (16.2 g) is dissolved in ethanol (60 ml). The mixture is stirred and thereto is added 3N sodium hydroxide (200 ml), and the mixture is stirred at 70° C. for one hour. After cooling, 6N hydrochloric acid (120 ml) is added to the mixture. The resulting white powdery precipitates are dissolved by adding thereto diethyl ether. The diethyl ether layer is separated and dried over magnesium sulfate and then concentrated under reduced pressure to give 2-(2,3,6-trifluorophenyl)acetic acid (13.9 g), as white crystals.

NMR (CDCl₃) δ: 3.79 (2H, s), 6.79-6.91 (1H, m), 7.02-7.18 (1H, m), 9.75 (1H, s)

REFERENCE EXAMPLE 74

Lithium aluminum hydride (0.8 g) is suspended in dry diethyl ether (5 ml) and the mixture is stirred. To the mixture is added dropwise a solution of 2-(2,3,6-trifluorophenyl)acetic acid (2.0 g) in dry diethyl ether (15 ml), and the mixture is refluxed for 30 minutes. To the reaction mixture are added water (0.8 ml), 10% aqueous sodium hydroxide (0.8 ml) and water (1.6 ml) in this order, and the mixture is stirred at room temperature. To the mixture is added diethyl ether (10 ml), and the resulting precipitates are separated by filtration and washed with tetrahydrofuran. The washing liquid and the filtrate are combined and then concentrated under reduced pressure to give 2-(2,3,6-trifluorophenyl)ethyl alcohol (1.9 g), as colorless oil.

NMR (CDCl₃) δ: 1.75 (1H, s), 2.98 (3H, t, J=6.7 Hz), 3.85 (2H, t, J=6.7 Hz), 6.74-6.87 (1H, m), 6.93-7.09 (1H, m)

REFERENCE EXAMPLE 75

To a solution of 2-(2,3,6-trifluorophenyl)ethyl alcohol (1. g) in methylene chloride (10 ml) are added with stirring p-toluenesulfonyl chloride (2.2 g) and triethylamine (2.0 ml), and the mixture is stirred at room temperature for 5 hours. The reaction mixture is poured into water and is extracted with diethyl ether. The ether layer is washed with aqueous saturated sodium hydrogen carbonate and aqueous saturated sodium chloride and dried over magnesium sulfate and then concentrated under reduced pressure. The resulting residue is purified by silica gel column chromatography (solvent, methylene chloride) and recrystallized from diethyl ether - n-hexane to give 1-[2-(p-toluenesulfonyloxy)ethyl]-2,3,6-trifluorobenzene (3.4 g), as colorless prisms, m.p. 73°-74° C.

NMR (CDCl₃) δ: 2.44 (3H, s , 3.03 (3H, t, J=6.5 Hz), 4.23 (2H, t, J=6.5 Hz), 6.70-6.82 (1H, m), 6.93-7.09 (1H, m), 7.29 (2H, d, J=8.5 Hz), 7.70 (2H, d, J=8.5 Hz)

REFERENCE EXAMPLE 76

Lithium aluminum hydride (5.6 g) is suspended in dry diethyl ether (70 ml) and thereto is added dropwise with stirring a solution of 1-[2-(p-toluenesulfonyloxy)ethyl]-2,3,6-trifluorobenzene (23.3 g) in dry diethyl ether (170 ml) at below 10° C., and the mixture is stirred at room temperature for one hour. To the reaction mixture are added water (5.6 ml), 10% aqueous sodium hydroxide (10.0 ml) and water (5.6 ml) in this order, and the mixture is stirred at room temperature for 30 minutes. The resulting white precipitates are filtered off, and the filtrate is concentrated under atmospheric pressure to give 2,3,6-trifluoro-1-ethylbenzene (13.2 g), as colorless oil.

NMR (CDCl₃) δ: 1.22 (3H, t, J=7.1 Hz), 2.72 (2H, q, J=7.1 Hz), 6.71-6.82 (1H, m), 6.87-7.03 (1H, m)

REFERENCE EXAMPLE 77

2,3,6-Trifluoro-1-ethylbenzene (1.09 g) is dissolved in conc. sulfuric acid (5.5 ml), and thereto is added with stirring a mixture of potassium nitrate (0.83 g) in conc. sulfuric acid (4 ml) at room temperature, and the mixture is stirred at the same temperature for one hour. The reaction mixture is poured into cold water (100 ml) and is extracted with diethyl ether. The ether layer is washed with aqueous saturated sodium chloride and dried over magnesium sulfate and then concentrated under reduced pressure to give 3-ethyl-2,4,5-trifluoro-nitrobenzene (1.14 g), as yellow oil.

NMR (CDCl₃) δ: 1.27 (3H, t, J=7.6 Hz , 2.77-2.89 (2H, m), 7.83 (1H, dd, J=8.0 Hz, 16.2 Hz)

EXAMPLE 1

To 6,7-difluoro-1-cyclopropyl-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid--B(OCOCH₃)₂ chelate (3.4 g) are added dimethylacetamide (10 ml) and 4-benzyl-3-methylpiperazine (6.8 g), and the mixture is reacted at 50° C. for 3 hours. After the reaction, the solvent is distilled off, and to the resulting residue are added acetone (30 ml) and conc. hydrochloric acid (5 ml), and the mixture is stirred at room temperature for 30 minutes. After the solvent is distilled off, to the residue is added water, and the crystals are separated by filtration. The aqueous layer is neutralized with sodium hydrogen carbonate and is extracted with dichloromethane. The dichloromethane is distilled off, and the resulting residue is purified by silica gel column chromatography (solvent, dichloromethane:methanol=20:1) and recrystallized from ethanol to give 7-(4-benzyl-3-methyl-1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (0.45 g), as pale yellow powder, m.p. 170°-171° C.

EXAMPLE 2

To 7-(4-benzyl-3-methyl-1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (0.30 g) are added acetic acid (10 ml) and 10% Pd-C (50 mg), and the mixture is subjected to catalytic reduction at 70° C. under atmospheric pressure for one hour. After the catalytic reduction, the reaction mixture is cooled and the catalyst is removed by filtration. The filtrate is concentrated, and to the residue is added water, and the mixture is adjusted to about pH 7.5 with sodium hydrogen carbonate, and then is extracted with dichloromethane. The dichloromethane is distilled off, and to the residue is added diethyl ether, and the resulting precipitates are separated by filtration and recrystallized from ethanol to give 7-(3-methyl-1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (0.16 g), as pale yellow powder, m.p. 206°-208° C.

EXAMPLE 3

To ethyl 1-cyclopropyl-7-(4-ethoxycarbonyl-1-piperazinyl)-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate (0.8 g) is added 10% aqueous sodium hydroxide (7 ml), and the mixture is refluxed for 5 hours. After cooling, the mixture is acidified with diluted hydrochloric acid and is extracted with dichloromethane. The aqueous layer is adjusted to about pH 7.5 with sodium hydrogen carbonate, and the resulting precipitates are separated by filtration to give 7-(1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (0.3 g), m.p. 291°-295° C. (decomp.).

NMR (DMSO-d6) δ: 8.84 (1H, s), 7.85 (1H, d, J=12.5 Hz), 4.30-4.48 (1H, m), 3.16-3.50 (8H, m), 2.78 (3H, s), 1.12-1.28 (2H, m), 0.84-0.96 (2H, m)

In the same manner as described in Example 3 using appropriate starting materials, there are prepared the same compounds as prepared in Examples 1 and 2.

EXPERIMENT (ANTIMICROBIAL ACTIVITY IN IN VITRO) The antimicrobial activity of the test compounds as mentioned below was tested by measuring minimum inhibitory concentration (MIC) by the serial dilution method on agar plate [cf. Chemotherapy, 22, 1126-1128 (1974)]. The microorganisms were used in a concentration of 1×10⁸ cells/ml (O.D. 660 mμ, 0.07-0.16) and 1×10⁶ cells/ml (100 folds dilution). When S. penumoniae type II and S. pneumoniae type III were used as the test microorganism, the medium contained 5% horse blood. The results are shown in Table 1. [Test compound]:

7-(3-Methyl-1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid

[Test microorganisms]:

A: Staphylococcus aureus FDA 209A

B: Staphylococcus pyrogens IID S-23

C: Staphylococcus pneumoniae type II

D: Staphylococcus pneumoniae type III

E: Pseudomonas aeruginosa E-2

F: Bacteroides fragilis GM7000

G: Eubacterium limosum ATCC 8496

H: Peptococcus anaerobis GM1003

I: Propionibacterium acnes ATCC 6919

J: Propionibacterium granulosum ATCC 25564

K: Enterococcus faecalis

                  TABLE 1                                                          ______________________________________                                                          Test Compound                                                 Test microorganisms                                                                            1 × 10.sup.6 cell/ml                                     ______________________________________                                         A               0.2                                                            B               0.39                                                           C               0.39                                                           D               0.39                                                           E               0.78                                                           F               0.2                                                            G               --                                                             H               0.39                                                           I               0.2                                                            J               0.2                                                            K               0.78                                                           ______________________________________                                     

What is claimed is:
 1. A compound of the formula: ##STR32## wherein R³ is C₁ -C₆ alkyl and R^(F) is C₁ -C₆ alkyl, or a pharmaceutically acceptable salt thereof.
 2. The compound according to claim 1, wherein R³ is methyl, or a pharmaceutically acceptable salt thereof.
 3. The compound according to claim 1, wherein R³ is methyl, and R^(F) is methyl, or a pharmaceutically acceptable salt thereof.
 4. An antimicrobial composition which comprises as an essential active ingredient an effective amount of a compound of the formula: ##STR33## wherein R³ is C₁ -C₆ alkyl and R^(F) is C₁ -C₆ alkyl, or a pharmaceutically acceptable salts thereof in admixture with a pharmaceutically acceptable diluent or carrier.
 5. The composition according to claim 4, wherein R³ is methyl, or a pharmaceutically acceptable salt thereof.
 6. The composition according to claim 4, wherein the active compound is 7-(3-methyl-1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid, or a pharmaceutically acceptable salt thereof.
 7. A method for the treatment of bacterial infectious diseases, which comprising administering an effective amount of the compound as set forth in claim 1 as an antimicrobial agent.
 8. The method according to claim 7, wherein the active compound is as set forth in claim
 2. 9. The method according to claim 7, wherein the active compound is 7-(3-methyl-1-piperazinyl)-1-cyclopropyl-6-fluoro-8-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acid, or a pharmaceutically acceptable salt thereof. 